There is known a nailing machine for continuously striking nails supplied to an inside of an injection port by a driver when the driver coupled to a piston is slidingly driven by impulsively driving the piston at an inside of a cylinder by compressed air as a power source. According to the nailing machine, the nailing machine is started by two operations of an operation of drawing a trigger lever formed at a base portion of a grip portion of grasping the nailing machine and an operation of pressing a contact arm arranged to be projected at a front end of the nose portion to a work. A nail is struck by the driver connected to the piston by driving the piston by compressed air introduced into the cylinder.
As types of striking a nail by such a nailing machine, there are a continuous striking mode for starting the nailing machine by pressing the contact arm to the work after operating to draw the trigger lever first and a single striking mode for starting the nailing machine by operating to draw the trigger lever after positioning the nose portion of the nailing machine at a struck portion of the work and operating the contact arm. In the continuous striking mode, the nailing machine is continuously started at each time of pressing the nose of the nailing machine to the work while operating to draw the trigger lever, as a result, nails are struck continuously. In the single striking mode, a nail is struck firmly to a determined position of striking. In addition thereto, in the single striking mode, twice striking or the like (dribble striking phenomenon), in which the nailing machine jumps up by a reaction and the nose portion is pressed again to the work to operate the contact arm, is not occurred.
There is an apparatus of starting a nailing machine of a background art in which the continuous striking mode and the single striking mode are automatically switched in the same nailing machine and a nailing operations are made to be able to be carried out in the respective modes. According to the nailing machine of the background art, a switch operating member is provided to move up and down integrally with the contact arm, in the single striking mode for operating the trigger lever after operating the contact arm, the switch operating member and the contact arm are maintained at upper positions by the trigger lever, by engaging the switch operating member or the contact arm maintained on an upper side and the contact lever, a valve stem of a start valve is maintained in an ON operating state, further, the valve stem of the start valve is made to be able to be operated up to an OFF position by resolving the switch operating member from being maintained by the operation of releasing the trigger lever.
In the single striking mode of driving the nailing machine by operating the trigger lever after operating the contact arm by pressing the nose portion of the nailing machine to a surface of the work, in order to prevent the dribble striking phenomenon in which when the nailing machine is started by operating the start valve ON by operating the valve stem by operating to draw the trigger lever, the contact arm is returned by moving upward the nailing machine by the reaction to separate the nose portion from the surface of the work and thereafter, when the nailing machine is moved down to operate the contact arm again, the nail is struck again, a position of making the start valve ON by operating the trigger stem of the start valve upward and a position of making the start valve OFF by moving the trigger stem of the start valve in the ON state in the lower direction are set to be shifted from each other such that the start valve is operated to be ON at an upper position of an operating stroke of the valve stem and such that the start valve is operated to be OFF at a lower position of the operating stroke of the valve stem. Further, according to the nailing machine having the switch operating member of the background art, a lower position of the valve stem of the start valve is restricted such that the valve stem maintains the ON state by the switch operating member, so far as the trigger lever is operated to draw, regardless of operating the contact arm upward and downward, the start valve is not made to be OFF and even when the contact arm is operated again, the nailing machine is prevented from being restarted. (JP-B2-2727960)
Meanwhile, when nails are struck continuously by the continuous striking mode, the contact arm is operated by an operation of pressing the nose portion to a face of the work by swinging down the nailing machine to the work in a state of operating to draw the trigger lever and a nail is struck by starting the nailing machine by making the start valve ON in the midst of swinging down. The continuous nail striking operation is made to be easy to carry out by absorbing the reaction produced when the nailing machine is driven by driving the nailing machine in this way while swinging down the nailing machine. When the start valve is set to be made ON at a portion of the operating stroke of the valve stem proximate to un upper dead center, the start valve is made ON at a final side of the operating stroke of the contact arm, and there is a case in which the nailing machine is driven after grounding the nose portion of the nailing machine which is swung down and the reaction cannot be absorbed, the large reaction is produced at the nailing machine and the nailing machine is considerably separated from the face of the work to deteriorate operability.
In order to reduce the reaction of the nailing machine in the continuous striking mode, it is necessary to operate the start valve ON at an early timing of the stroke of the contact arm, however, in order to make the start valve operated to be ON at an early timing, it is necessary to set the position for making the valve stem ON in the lower direction of the stroke. However, when the position of making the valve stem ON is set to be proximate to a side of a lower dead center, the amount of shifting the ON position and the OFF position of the valve stem is reduced. Therefore, there is brought about the dribble in which the contact arm is returned when the nailing machine is moved upward by the reaction in the single striking mode as described above, at that occasion, the start valve is brought into the ON state by moving down the valve stem to the OFF position and the nailing machine is driven again by operating the contact arm again. Or there is a case in which after operating the contact arm in a state in which air is not supplied to the nailing machine, in a state of maintaining the single striking mode by operating to draw the trigger lever, the valve stem of the start valve is arranged upward from the ON position by the switch operating member and therefore, when an air chuck is connected under the state, the start valve is operated to be ON to erroneous operate the nailing machine.